I pass so many cyclists on my commute most days that greeting them would like trying to wave to every car driver on the road. I tend to glance up and see if they're one of the regulars, though. But if I'm biking in the woods and haven't seen anyone for an hour or two of course I'll look up and smile if I see someone, on foot or cycling. It really depends on the surroundings.
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett